If I remember correctly move in is the weekend before orientation starts. If you do the summer biochem it's probably the weekend before that.
Yeah, there is a long waitlist for studio apartments, most people on it get one by M3. That's unless you're married/have a partner, or are an MD/PhD as they all get priority for studios.
Roommates are usually randomly assigned (there's some kind of application with various preferences you fill out to match people up) but I think you could probably request a roommate if you knew someone. You can get assigned other incoming M1s or upperclassmen who have a roommate vacancy. It usually tends to work out well - I've heard of very few people with roommate problems.